Physiology of Hearing

Question 1

sound is a series of?

Answer 1

of sound waves

Question 2

in a compressible medium, such as air, what happens to the pressure waves of sound?

Answer 2

the pressure waves cause the molecules of the medium to compress together and pull apart alternately

Question 3

in an incompressible medium such as water/solids - what happens to the pressure waves of sound?

Answer 3

the pressure wave propagates by direct interaction of the particles
they effectively bump into one another

Question 4

the waves propagate through?

Answer 4

Through the medium, but the molecules themselves do not change their mean distance from the source

Question 5

velocity of sound wave in air =

Answer 5

340 m/s

Question 6

velocity of sound wave in water =

Answer 6

1500 m/s

Question 7

what is a sound’s frequency?

Answer 7

measured in Hz
it is the number of oscillations per second

Question 8

what is a sound’s wavelength?

Answer 8

measured in m
it is the distance between points of maximal pressure

Question 9

what is a sound’s volume?

Answer 9

measured in dB (logarithmic)
it is the difference in pressure between maximal and minimal pressures

Question 10

what does the pinna do?

Answer 10

it directs sounds into the auditory canal (acoustic meatus)

Question 11

what does the external ear consist of?

Answer 11

it consists of a vertical portion and a horizontal portion

Question 12

what does the auditory canal limit?

Answer 12

it limits the frequencies that reach the tympanic membrane (aids with identifying sound direction)

Question 13

what does the auditory canal contain?

Answer 13

contains glands that secrete cerumen (earwax) and small hairs to trap debris

Question 14

what does the tympanic membrane do?

Answer 14

it separates the ear canal from the middle ear and is the first part of the sound transducing mechanism

Question 15

what is the external ear shaped like?

Answer 15

shaped somewhat like a loudspeaker cone (which is an ideal shape for transmitting sound between solids and air)

Question 16

middle ear cavity extends to?

Answer 16

extends into tympanic bulla
(outcropping of temporal bone)

Question 17

what is the middle ear connected to and by what?

Answer 17

connective to nasopharynx by auditory tube (Eustachian tube)

Question 18

auditory ossicles?

Answer 18

malleus
incus
stapes

Question 19

what does the middle ear allow for?

Answer 19

allows for balance of changes in atmospheric pressure - blockage of the auditory tube can impede hearing and be painful

Question 20

where is the inner ear embedded?

Answer 20

within the temporal bone

Question 21

what does the inner ear consist of?

Answer 21

of cochlea
vestibulum
semi-circular canals

Question 22

what is the stapes attached to - inner ear?

Answer 22

attached to oval window - transduces vibrations of the ossicles to the fluid within the vestibulum and cochlea

Question 23

what cells does the cochlea contain?

Answer 23

sensory cells

Question 24

impulses from cochlea transmitted via?

Answer 24

via the cochlear nerve branch of vestibulocoChlear nerve (cranial nerve VIII) to the brain

Question 25

fluid filled semi-circular canals and vestibule contain what kind of sensors?

Answer 25

sensors on head position and movement

Question 26

impulses from canals transmitted via? inner ear

Answer 26

via the vestibular nerve branch of vestibulocochlear nerve (cranial nerve VIII) to the brain

Question 27

when tympanic membrane vibrates, what happens to the waves?

Answer 27

the waves are transmitted via the ossicles onto the oval window

Question 28

what is the oval window?

Answer 28

it is a membrane held in place by annular ligaments that allow it to bulge into the cochlear

Question 29

if the ossicle are pulled away, what does it cause?

Answer 29

it causes the changes in the opposite direction

Question 30

repeated transmission of sound waves occurs along?

Answer 30

along the basilar membrane

Question 31

movement of the basilar membrane causes?

Answer 31

causes the tectorial membrane of the sensory structure to be displaced

Question 32

what are not the same along the entire basilar membrane?

Answer 32

amplitudes and sensitivity of the wave are not the same along it

Question 33

what does frequency discrimination depend on?

Answer 33

depends on the sound frequency

Question 34

high frequency waves have maximum amplitude near?

Answer 34

near the round window and do not travel far

Question 35

low frequency waves cause the basilar membrane to vibrate with?

Answer 35

with maximal amplitude near the tip of the cochlea

Question 36

organ of corti is what type of structure?

Answer 36

a sensory structure

Question 37

what do travelling waves move?

Answer 37

they move basilar membrane up and down in response to sound stimulation

Question 38

the tectorial membrane is displaced relative to?

Answer 38

relative to the hair cells

Question 39

travelling sound waves causes sensory hair bundles to be?

Answer 39

to be bent back and forth at a right angle to the canal

Question 40

structure of sensory hairs?

Answer 40

they are longer toward the tip of the tectorial membrane - stereocilia

Question 41

as basilar membrane moves upwards - what happens to hair cells?

Answer 41

hair cells bent towards longest hair

Question 42

as basilar membrane moves downwards - what happens to hair cells?

Answer 42

hair cells bent towards shortest hair

Question 43

there are three semi-circular cells why?

Answer 43

one for each dimension

Question 44

each canal has an ampulla - what is that and what is it containing?

Answer 44

ampulla (enlargement) containing hair cells in one wall

Question 45

the hair cell stereocilia project out into a?

Answer 45

into a gelatinous cupula

Question 46

what happens to the vestibular system when an animal moves its head?

Answer 46

the endolymph within the semi-circular canals lags due to inertia

Question 47

the lag of the endolymph pushes the what?

Answer 47

pushes the cupula